In the following paragraphs, prior art references pertaining to the subject matter of the application are set out.
German Patent Publication No. DE 195 43 080 A1 discloses a hydraulically operated fuel injection valve for a gas engine. One disadvantage of hydraulically operated valves is the comparatively slow response characteristic.
German Patent Publication No. DE 100 52 336 A1 discloses a fuel injection valve that is hydraulically opened, whereby the hydraulic pressure is controlled by means of an electromagnetic or piezoelectric control valve. But the response characteristic and the scope of control options, in particular with respect to multiple injections or the shaping of the injection behavior, are not optimal.
German Patent Publication No. DE 101 29 375 A1 discloses an injector with a piezoelectric actuator, which acts on a control valve, if necessary via a transmission device, to control the injection of liquid fuel through a needle valve. The piezoelectric actuator consists of a stack of piezoelectric elements, whereby the piezoelectric element adjacent to the control valve is executed as a sensor to detect contact between the piezoelectric actuator and the control valve or to detect the opening of the control valve. The design of this injector is not suitable for the injection of gaseous fuel.
German Patent Publication No. DE 199 29 589 A1 discloses an injector with a piezoelectrically actuated control valve, which in turn hydraulically controls a needle valve for the injection of liquid fuel. Also provided is an electrical assembly to determine whether the control valve has opened, to calibrate the piezoelectric actuator, or to compensate for temperature related variations.
German Patent Publication No. DE 199 05 340 A1 discloses a method and a device to adjust and re-adjust electrical piezoelectric actuators, whereby a direct voltage is applied to the piezoelectric actuator to set a desired idle lift between the piezoelectric actuator and a valve actuating element, whereby if necessary a control voltage, for example a pulsed control voltage, can be superimposed onto the direct current voltage, and whereby the direct current voltage effects a longitudinal deformation of the piezoelectric actuator that is independent of the control voltage, wherein “lift” is the distance moved by the valve actuating element from a closed position.
German Patent Publication No. DE 198 57 615 C1 discloses a lever transmission to transfer the force resulting from displacement of an actuator to a final control element, in particular in an injection valve. The lever transmission is in contact with the actuator and the final control element via sliding elements, whereby the contact surfaces to the sliding elements or a thrust bearing are executed to have convex or concave shapes, respectively, and whereby the radii of the associated surface areas are matched in order to reduce surface pressure.
German Patent Publication No. DE 101 30 857 A1 discloses a fuel injector with piezoelectric elements that are in contact with a stud-like positioning element, and by means of the positioning element can actuate a following valve element to open or close an injection opening. When the injection opening is closed, the distance between the positioning element and the valve element preferably is measured by means of a scanning coil and regulated to a desired value, in order to be able to compensate for thermal expansion under different operating conditions and for mechanical deformation for differing fuel pressures and loads.
German Patent Publication Nos. DE 101 20 709 A1 and DE 102 20 498 A1 disclose fuel injection valves that comprise a piezoelectric actuator and a single transmission device that comprises a single lever.
German Patent Publication No. DE 197 57 659 C1 discloses an injection valve with a piezoelectric actuator and a valve element that can be actuated via two transmission elements switched in parallel. A compensating element with a curved face is arranged between the transmission elements and the piezoelectric actuator, in order to compensate for a tilting of the piezoelectric actuator and for differing overall heights of the transmission elements.
German Patent Publication No. DE 101 01 799 A1 discloses a fuel injection valve, in particular for a common rail system, whereby a piezoelectric actuator acts via a disc-shaped actuating element upon two kidney-shaped valve lifters, which in turn actuate a valve element.
Valve devices known in the art have the disadvantage that in the opened valve state the aperture cross section defined by the valve lift and the valve geometry is comparatively small, so that for the injection of gaseous fuel very high gas pressures are necessary to supply an adequate quantity of fuel into an associated combustion chamber or space. For this reason there is a need for a valve device that allows an adequate supply of gaseous fuel during full-load operation but also allows very short injection periods at idle speeds or at low engine loads.
Furthermore, there is a need for a valve device and a method for the injection of gaseous fuel into the combustion chamber of an internal combustion engine that allows a simple and cost-effective design and a rapid response behavior, and in particular allows multiple injections of fuel or injections with interruptions during one power cycle and/or the shaping of the injection behavior over an injection period.
An objective of the present technique is to provide a valve device and a method for the injection of gaseous fuel into the combustion chamber of an internal combustion engine and the use of spring(s) in a valve device to allow the following: An adequate supply of gaseous fuel, in particular during full load operation of the engine; A simple, cost-effective, and wear-resistant design and/or a rapid response behavior as well as a variable valve lift. In particular, multiple or interrupted injections of fuel during one power cycle and/or a shaping of the injection behavior during the injection period.